=encoding utf8

=head1 NAME

pds.db - small database with planar difference set samples

=head1 VERSION

This is version 1.0 of the database, created on July 30, 2019.

=head1 DESCRIPTION

This file is the default database distributed with the Perl 5 module
Math::DifferenceSet::Planar.

It contains 604 cyclic planar difference sets with orders ranging from
2 to 4096.  The sets are chosen minimal by lexicographic ordering.

=head1 FILE FORMAT

SQLite 3.x database.

=head1 SCHEMA

  CREATE TABLE difference_set (
    order_   integer NOT NULL PRIMARY KEY,
    base     integer NOT NULL,
    exponent integer NOT NULL,
    modulus  integer NOT NULL,
    n_planes integer NOT NULL,
    deltas   blob    NOT NULL
  );

=head1 DATA REPRESENTATION

If I<D = { d_1, d_2, ..., d_k } (mod m)> is a canonical cyclic
planar difference set of order I<k - 1> with I<d_1 E<8801> 0> and
I<d_2 E<8801> 1 (mod m)>, I<deltas> is a sequence of I<k - 2> numeric
values packed in 'w*' format, calculated as differences of consecutive
residue values of I<D> starting with I<d_3 - d_2>.  The difference of
the smallest two values in a canonical set is always 1 and thus not
important to store.

=head1 PROVIDER

Martin Becker, E<lt>becker-cpan-mp I<at> cozap.comE<gt>

=head1 COPYRIGHT AND LICENSE

The contents of this database are mathematically defined entities.
The provider believes mathematical constants not to be proprietary or
subject to copyright legislation, although the software used to calculate
them may be.

=cut
